Abstract
Articular cartilage pathologies are a major public health problem today. To date, there is no treatment that can repair the cartilage. However, among the therapeutic approaches currently being evaluated, tissue engineering, the objective of which is the formation of neo-tissues, seems to be a promising therapeutic solution.The final objective of this thesis project concerns the development of an injectable genetically activated matrix (MGA), making it possible to control the hypertrophic chondrocyte differentiation of mesenchymal stromal cells (MSCs). To carry out this project, the first objective was to find a nucleic acid vector suitable for the development of an MGA and capable of efficiently transfecting MSCs. We therefore designed a new siRNA nanovector, called solvent exchange lipoplexe formulation (SELF), which has a tunable size, is stable over time in cell culture conditions and possess a high efficiency to transfect primary human mesenchymal stromal cells. We associated SELF with porous collagen 3D microspheres and demonstrated that loading efficiency and release kinetics are correlated with SELF size. This original and unique type of gene activated matrix, with adaptable release kinetics, could be of interest for long-term and/or sequential transfection profiles of stem cells in 3D culture. Thus, we formed different MGAs capable of inducing different inhibition profiles of a specific gene over at least 21 days. Finally, we studied the efficiency of MGA on an in vitro model of chondrocyte differentiation of human MSCs. We have shown that MGA induces a prolonged inhibition of Runx2 gene expression for at least 21 days. Under chondrocyte differentiation conditions, this decrease in Runx2 expression seems to decrease the expression of certain markers of hypertrophy. Despite these promising results, an inhibitory effect of MGA on MSC differentiation remains to be verified. In summary, our work has shown the interest of our approach to control the expression of hypertrophic markers of a neocartilage. More precise control of vector release should improve the efficiency of MGA for cartilage tissue engineering applications.